Proficiency Exam

Question 1

What is the simplest form of monosaccharide?

Answer 1

triose

Question 2

What are the two trioses? Differentiate.

Answer 2

Glyceraldehyde - simplest aldose
Dihydroxyacetone - simplest ketone

Question 3

What forms upon the reaction of an aldehyde with an alcohol? Draw and explain the mechanism.

Answer 3

A hemiacetal.

1.) The electrophilic oxygen in the alcohol group attacks the electrophilic carbonyl carbon.
2.) Upon the nucleophilic attack of the carbonyl carbon, electrons from the pi bond move towards the oxygen, and will form a negative charge.
3) The oxygen from the R-OH that attached to the carbonyl will have a positive charge.
4.) The intermediate is formed (which is unstable since there are negative and positive charges in the molecule).
5.) There will be a proton transfer (from the positively charged O to the negatively charged O).
6.) The hemiacetal is now formed.

Question 4

A six-membered ring is called?

Answer 4

pyranose

Question 5

a five-membered ring is called?

Answer 5

furanose

Question 6

Cyclization from C1 to C5 of an aldohexose or C1 to C4 of an aldopentose forms a?

Answer 6

Cyclic hemiacetal

Question 7

The monosaccharides can undergo interconversion between alpha and beta forms, using the open-chin structure as an intermediate. What is the process called? What do you call the enzymes that catalyze the reaction?

Answer 7

Mutarotation; Mutarotases

Question 8

Sketch the Fischer and Haworth projections (pyranose and furanose form) of the following compounds:

D-xylose
D-arabinose
D-glucose
D-psicose

Answer 8

Answer on paper

Question 9

What is the relationship of D-gulose and D-glucose in terms of stereochemistry?

Answer 9

diastereomers

Question 10

[You can memorize the aldohexoses by hand]. Give all the C2 epimers.

Answer 10

D-Allose and D-Altrose
D-glucose an D-mannose
D-gulose and D-idose
D-galactose an D-talose

Question 11

True or False. Only the furanose form is possible for ketopentoses.

Answer 11

True

Question 12

Cyclization using C2 to C5 results into?

Answer 12

Hemiketal formation

Question 13

In the conversion of Fischer projection to Haworth projection, what becomes the anomeric carbon?

Answer 13

The C1

Question 14

Differentiate the alpha and beta anomers?

Answer 14

beta = cis
alpha = trans

Question 15

Differentiate the configurational isomers

Answer 15

Enantiomers = nonsuperimposable mirror images
Diastereomers = nonsuperimposable, non-mirror images of one another
Anomers = stereoisomers that differ in the configuration at the anomric carbon
Epimers = stereoisomers that differ in the configuration at one carbon OTHER than the anomeric carbon

Question 16

The resulting product when an aldose is oxidized using a mild oxidizing agent. What is being oxidized?

Answer 16

Aldonic acid, carbonyl carbon

Question 17

The resulting product when an aldose is being oxidized using a strong oxidizing agent? What is being oxidized?

Answer 17

Aldaric aicid, C1 and C6

Question 18

What is the product if an aldose is being oxidized at C6 via enzyme catalyzed reaction?

Answer 18

Alduronic (Uronic) Acid

Question 19

Reduction of the carbonyl group on the sugar gives rise to the class of polyhydroxycompounds called ____?

Answer 19

Alditols

Question 20

Elimination of water between the anomeric hydroxyl of a cyclic monosaccharide and the hydroxyl group of another compound yields to the formation of:

Answer 20

O-glycoside

Question 21

What is sucrose?

Answer 21

The final product of photosynthesis, used as a primary energy source in many organisms. It is a disaccharide made up of alpha-glucose that is glycosidically linked to beta-fructose via alpha 1-2 glycosidic bond

Question 22

A major animal energy source that is connecte via beta (1>4) glycosidic bond between glucose and galactose

Answer 22

Lactose

Question 23

A major circulatory sugar in insects; use for energy. It is conneected via alpha (1>1) glycosidic bond between glucose and glucose

Answer 23

alpha-alpha trehalose

Question 24

The dimer derived from the starch and glycogen polymers. It is an alpha (1>4) glycosidic bond between two units of glucose

Answer 24

maltose

Question 25

The dimer of a cellulose polymer. It is connected via beta (1>4) glycosidic bond between two glucose units

Answer 25

cellobiose

Question 26

A constituent of plant glycosides and some polysaccharides. It is connected via beta (1>6) glycosidic bond between two units of glucose

Answer 26

gentiobiose

Question 27

What are homopolysaccharides?

Answer 27

a polysaccharide that contains only one kind of monosaccharide.

Question 28

What are heteropolysaccharides?

Answer 28

A polysaccharide that is made up of several monosaccharides

Question 29

what are the storage molecules?

Answer 29

starch and glycogen

Question 30

what are the storage polysaccharides?

Answer 30

amylose and amylopectin

Question 31

difference between starch and glycogen

Answer 31

starch = energy storage in plants glycogen = energy storage in animals

Question 32

differentiate the structure of amylose and amylopectin

Answer 32

amylose = continuous, unbranched chains of up to 4000 alpha D-glucose units joined by alpha (1>4) glycosidic bonds amylopectin = highly branched polymer consisting of 2430 units of D-glucose joined by alpha (1>4) glycosidic bonds and branches created by alpha (1>6) glycosidic bonds

Question 33

explain the structure of glycogen

Answer 33

-it constitutes up to 10% of liver mass and 1-2% of muscle mass -alpha (1>6) branches for every 8-12 residues -gives red-violet color with iodine

Question 34

Draw the structure of galacturonic acid

Answer 34

.

Question 35

When an aldose is being oxidized using a mild oxidizing agent, the carbonyl carbon becomes a COOH, leading to the formation of aldonic acid. Aldonic acid is said to have an equilibrium with?

Answer 35

Lactones (cyclic carboxylic esters)

Question 36

Why is it that humans, even if they are starving, cannot utilize enormous quantities of glucose in the form of cellulose (i.e., why can't humans gain energy if they eat plants?)

Answer 36

Because humans do not have enzymes that can catalyze the cleavage between the beta-(1>4)-glycosidic linkage

Question 37

What are the structural molecules

Answer 37

Chitin and cellulose0

Question 38

It is the major structural component of the exoskeletons of invertebrates, such as insects, crustaceans, and also occurs on the cell walls of fungi, algae, and yeasts. It is joined by beta-(1>4) glycosidic bond of N-acetyl-beta-D-glucosamine

Answer 38

chitin

Question 39

These sugars are formed by mild reduction of sugars

Answer 39

sugar alcohols

Question 40

Formerly called as mucopolysaccharides

Answer 40

glycosaminoglycans

Question 41

Chondroitin sulfates, keratan sulfates of connective tissues, dermatan sulfates of skin, and hyaluronic acid are polymers of repeating disaccharide units of?

Answer 41

N-acetylgalactosamine

Question 42

Draw the structure of beta-D-galactosamine

Answer 42

.

Question 43

These are monosaccharides with one or more hydroxyl groups replaced by hydrogens

Answer 43

Deoxy sugars

Question 44

The ribose moeity of nucleotides such as ATP and GTP is phosphorylated at what position

Answer 44

5' position

Question 45

an enzyme that catalyzes the hydrolysis of alpha-(1>4)-glycosidic bonds

Answer 45

amylases

Question 46

an exoglycosidase and cleaves the alpha-(1>4) linkages from the nonreducing end of the polymer

Answer 46

beta-amylase

Question 47

an endoglycosidase and hydrolyzes the alpha-(1>4)-glycosidic linkages along the chain to produce glucose and maltose

Answer 47

alpha-amylase

Question 48

catalyze the hydrolysis of alpha-(1>6)-glycosidic bonds

Answer 48

debranching enzymes

Question 49

Formed by bacteria that are components of dental plaque

Answer 49

dextrans

Question 50

These are found in cell walls of nearly all plants. It is the major structural component of plants, especially wood and fibers. -most abundant natural polymer

Answer 50

cellulose

Question 51

almost a pure cellulose

Answer 51

cotton

Question 52

Explain the structure of cellulose

Answer 52

-a linear polymer of approximately 2800 D-glucose units per molecule joined by beta-(1>4)-glycosidic bonds -fully extended conformation with alternating 180 deg flips of glucose units

Question 53

A polymer of D-galacturonic acid joined by alpha-(1>4)-glycosidic bonds

Answer 53

Pectin

Question 54

These are polysaccharides based on a repeating disaccharide unit where one of the monomers is an amino sugar and the other has a negative charge due to a sulfate or carboxylate group

Answer 54

glycosaminoglycans

Question 55

a natural coagulant that has a structure of D-glucuronic acid-2-alpha-(1-4)-N-sulfo-D-glucosamine-6-sulfate

Answer 55

heparin

Question 56

a component of vitreous humor of the eye and the lubricating fluid of joints and has a structure of D-glucuronic acid-beta(1>3)-N-acetyl-D-glucosamine

Answer 56

hyaluronic acid

Question 57

components of tendons, cartilage, and other connective tissues

Answer 57

chondroitin sulfate and keratan sulfate

Question 58

Component of the extracellular matrix of skin

Answer 58

dermatan sulfate

Question 59

structure of heparin

Answer 59

D-glucuronic acid-2-sulfate-alpha-(1>4)-N-sulfo-D-glucosamine-6-sulfate

Question 60

structure of hyaluronic acid

Answer 60

D-glucuronic acid-beta-(1>3)-N-acetyl-D-glucosamine

Question 61

structure of chondroitin sulfate

Answer 61

D-glucuronic acid-beta-(1>3)-N-acetyl-D-galactosamine-4-sulfate

Question 62

structure of keratan sulfate

Answer 62

D-galactose-beta-(1>4)-N-acetyl-D-glucosamine-6-sulfate

Question 63

these contain carbohydrate units covalently bonded to a polypeptide chain

Answer 63

glycoproteins